The invention is directed to the field of badge type electrochemical gas trace sensors and particularly one using a thin layer electrochemical cell with large area thin film sensing electrode formed on a porous membrane in contact with a very thin layer of nonaqueous aprotic organic based electrolyte solution.
The present invention is related to a copending application of the present applicant, Ser. No. 557,037 (now abandoned) entitled "An Electrochemical Sensor for Multiagent Detection on Aprotic Organic Electrolyte Solution," assigned to the same assignee as the present invention, filed Dec. 1, 1983, and to a copending application Ser. No. 570,152 (now abandoned) of H. V. Venkatasetty and J. D. Zook, entitled "Electrochemical Passive Chemical Agent Detector," assigned to the same assignee as the present invention, and filed Jan. 12, 1984, and the teachings of both of which are incorporated herein by reference.
Electrochemical gas sensors require a structure to contain the electrolyte. It is important that the structure be efficient in transferring the molecules to be sensed to the working electrode without being trapped at surfaces where they are precluded from reaching the working electrode. In the second copending application cited above a badge type electrochemical sensor with a nonaqueous electrolyte solution is designed as a small thin sandwich cell configuration which employs a working electrode of platinum film on a gas and vapor molecule permeable polymer membrane, with two counter electrodes of platinum film and a suitable reference electrode such as Ag/Ag.sup.+.
The present invention is particularly directed to a thin-layer electrochemical cell with a large area thin film sensing electrode in contact with a very thin layer of electrolyte (.about.10.sup.-2 mm) with counter and reference electrodes suitably placed. Electrochemical oxidation or reduction of the electroactive chemical, toxic chemical or chemical agent can be quantitatively completed in less than two seconds. Using nonaqueous aprotic organic based electrolyte solutions with wide voltage window in which chemical agents are more soluble, the cell can be used for multiagent detection with improved sensitivity.